Art of continuous distillation



April 29, 1930. ooms 1,756,032

ART OF CONTINUOUS DISTILLATION Original Filed June 8, 92

ece'wevs PUMP QonAehsev H eater PUMP Nachniel E Loomis.

exm Patented Apr. 29, 1930 UNITED STATE PATENT OFFICE" NATHANIEL E. LOOMIB, OI 'WESTFIELD, NEW JERSEY, ASSIGNOR TO STANDARD OIL DEVELOPMENT COMPANY, A CORPORATION OF DELAWARE ART OF CONTINUOUS DISTILLATION Application filed .Tune 8, 1922, Serial No. 586,748. Renewed Kay 17, 1888.

My invention relates to the art of continuous distillation, and more particularly to continuous vacuum distillation. The invention will be fully undertsood from the following description, in connection with the accompanying drawing which represents diagrammatically an illustrative form of the apparatus features contemplated.

In the drawing, the reference character 1 designates a heating conduit or coil arranged in relation with any suitable source of heat, as by being mounted in a suitable furnace chamber, and having a feed-inlet pipe 2, and an outlet pipe 3 discharging into a frictionating tower at at a suitable point, but ordinarily preferably above one or more of the lowermost plates, so as to introduce the hot material from the heating conduit or coil into an intermediate zone of the series of fractionating zones represented in the tower. The internal construction of the tower may comprise for example, plates 5 having bellcaps or vapor distributors, and reflux tubes 6, and at the upper end a partial-condenser section comprising a pair of tube sheets 7 with, tubes 8 therebetween for passage of vapors the space surrounding the tubes having inlet and outlet pipes 9 and 10 respectively, as will. be referred to more particularly hereafter. From the top vapor space a pipe 11 leads to an end condenser 12 connected in turn to receivers 13, and 19, adaptable to be used in relay.

From the base of the tower 4 a pipe 14 in which is connected a pump 15 leads to a second heating conduit or coil 16. A discharge line therefrom leads to preferably an intermediate zone of a second fractionating tower 17 which may advantageously be of the same general construction as the tower 4; the bottom discharge line 18 thereof leading to a tank if only a two-tower plant is used, orto the next heating conduit Where a more extensive battery is employed. The tower 17 has in connection with its vapor off-take 27 an end condenser, receivers, and vacuum pump as in the case of the first tower, (these not being shown, for simplification) andits partial condenser 20 is also provided with inlet and outlet pipes 21, 22.

In operation, the liq uidto be distilled, for exam e an oil which is to be fractionated is intro uced through pipe 2. Various hydrocarbons in particular may be advantageously operated upon, such as crude petroleum or distillates, or stocks from cracking-installations, but I may refer, as an example, to the preparation of lubricating fractions of petroleum. The oil in this case may have been already topped of its lighter fractions, or where using a battery of a suitable number of units, the crude may be used. The oil is heated in the heating conduit or coil to a I temperature sufficient to allow vaporization to an adequate extent when discharged into the tower 4. The particular temperature necessary will of course vary with the stock used, but on lubricating fractions, the temperature will be held down below cracking range by putting the vacuum-pump 23 into action. Vapors pass up and through the layers of condensate which collect on the plates, the amount of reflux necessar being-further provided by the artial con enser above. Separation of the ighter and heavier constituents goes 'on in the tower, becoming sharper and sharper from plate to plate, the lighter fraction esca ing past the partial condenser as vapor an passing on over to condense in the end condenser 12. The heavier fraction collecting at the bottom of the tower is passed by the pump 15 to the next heating-coil 16 maintained at progressively higher temperature and thence to the tower 17. Vapors leaving this tower and partial condenser proceed to the end condenser therefor, while the heavy fraction collecting at the bottom of the tower is passed on to the next unit in the battery, or to a tank, as the circumstances may determine.

In the regulating of the temperatures of the partial condensers for lubricating distillates I prefer to introduce steam of the proper temperatures respectively, by the inlet-pipes 9 and 21. When fractionating light stocks however, water may be used or in some cases it is advantageous to use the incoming cold feed-oil, passing it through the partial condenser on its way to the heating coil 1.

For the supply of additional heat as need- 24 and 25 in open or closed coils as preferred.

In some circumstances it is advantageous however to utilize Oll by-passed from the next hotter coil, as for example by taking some of the discharge from coil 16 oil through pipe 26 to the bottom of the tower 4.

From the foregoing it will be seen that marked efiiciency and economy in operation are attained, since the distillates are mostly vaporized directl and indirect vaporization by secondarily a ded heat is depended upon rather for the removal of dissolved traces of lighter fractions. Moreover, the time during which stocks are heated is reduced to a mimmum and correspondingly the risk of cracking is diminished, a matter which is of paramount importance in dealing with lubrieating fractions.

Furthermore, in using a vacuum with a feed as described a low pressure can be obtained at the feed plate and correspondingly a more efficient vaporization in spite of the fact that plate-towers are used.

Although I have described my invention by reference to specific details, itwill be understood that these are illustrative and not limitative. Nor is the invention to be understood as dependent upon the accuracy of any theories or reasons suggested to explain the advantageous results. On the contrary the invention is to be regarded as limited only in the following claims, in which it is my intention to claim all inherent novelty as broadly as the prior art permits.

What I claim is 1. The improvement in the art of distilling petroleum hydrocarbons which comprises passing the hydrocarbons throu gh a conduit in which they are heated to a temperature at which vaporization tends to occur, thence into a vapor-liquid separating zone, withdrawing therefrom the lighter constituents as vapor and the heavier constituents as liquid, imparting additional. heat to heavier constituents in said zone by heating in a conduit and returning a part of said withdrawn heavier constituents, and withdrawing the vapors thereby evolved with said lighter constituents.

2. Method according to claim 1, in which a portion of the vaporized lighter constituents and a portion of the vapors evolved from the heavier constituents are condensed and refluxed.

3. Method according to claim 1, imwhich the vapors evolved in the separating zone are condensed in part and refluxed to the unvaporized heavier constituents.

4. The improvement in the art of obtaining lubricating fractions from a mixture of petroleum hydrocarbons, which comprises passing the hydrocarbons through a conduit in which they are heated to a temperature at which vaporization tends to occur, thence into a zone of pressure substantially less than that which prevails in the conduit, withdrawing therefrom lighter constituents as Vapor and heavier constituents as liquid, imparting additional heat to heavier constituents in said zone by heating and returning a part of said withdrawn heavier constituents, and withdrawing the vapors thereby evolved with said lighter constituents.

5. The improvement in the art of distilling petroleum hydrocarbons, which comprises passing the hydrocarbons through a heating conduit, thence into an intermediate zone of a fractionating tower, fractionating and separating oli lighter constituents as vapor and heavier constituents as liquid, passing said liquid through a further heating conduit of higher temperature, thence into an intermediate zone of a fractionating tower, and fractionating and separating oil lighter constituents as vapor and heavier constituents as liquid while supplying heat at the bottom of the first mentioned tower by introducing hot hydrocarbons from the last mentioned heating conduit.

6. The improvement in the art of obtaining lubricating fractions from a mixture of hydrocarbons, which comprises passing the hydrocarbons through a heating conduit, thence into an intermediate zone of a fractionating tower, maintaining a pressure less than atmospheric in the tower, fractionating and separating oft lighter constituents as vapors and heavier constituents as liquid, passing said liquid through a further heating conduit of higher temperature. thence into an intermediate zone of a fractionating tower, maintaining a pressure less than atmospheric in the last mentioned tower, fractionating and separating oflt' lighter constituents as vapor and heavier constituents as liquid. and delivering hot hydrocarbons from the last mentioned heating conduit to the bottom of the first mentioned tower to supply heat thereto.

7. A distillation apparatus which com-'- prises a heating conduit, a fractionating tower of the plate-containing type into which said conduit discharges at a point above the lower plates, a partial condenser at the top of said tower, means for withdrawing the liquid from the bottom of the tower, a conduit for heating the withdrawn liquid and for returningit to the tower in contact with liquid collecting therein, and means for taking off vapors from the tower.

8. A distillation apparatus which comprises a heating conduit, a fractionating tower into which said conduit discharges at a point above the lower plates, a partial condenser at the top of said tower. an end condenser for receiving vapors passing therelit? beyond, a further heating conduit for receiving liquid from the bottom of said tower, a further fractionating tower into which said last mentioned heating conduit discharges at a point above the lower plates, a partial condenser at the top of said last mentioned tower, an end condenser for receiving vapors passing therebeyond, and a connection from the discharge of the last mentioned heating conduit into the bottom of the first mentioned fractionating tower.

9. A distillation apparatus according to claim 8 with the further addition of means to maintain. a pressure of less than atmospheric in the fractionating towers.

10. The method of distilling hydrocarbon oils comprising passing the oil in a confined stream through a heating zone, discharging the oil into a separating chamber, passing 2 the unvaporized oil in countercurrent to a current of steam, subsequently subjecting said steam with the vapors from the separating chamber to refluxing action, and maintaining sub-atmospheric pressure on the-systern.

11. The method of distilling hydrocarbon oils which comprises passing the oil in an externally heated confined stream through a heating zone, discharging the oil into an unheated separating chamber, supplying steam in said chamber so as to pass through the liquid therein, removing separated vapors and steam from said chamber, and subjecting the'removed vapors and steam to a controlled refluxing action.

12. The method of distilling hydrocarbon oils which comprises passing the oil in an externally heated confined stream through a heating zone, discharging the oil into an un- 40 heated separating chamber, supplying steam in said chamber so as to pass through the liquid therein, removing se arated vapors and steam from said cham 'er, subjectin the removed vapors and steam to a controlled refluxing action and returning reflux to the separating chamber.

NATHANIEL E. LOOMIS. 

